[Khill]

one i have found quite useful is the scangauge2, It is more intended to be rather "installed" in one vehicle, but it can be taken around to others. What makes this one interesting is that not only does it read codes but it also acts as digital gauges (rpm,mph,iat,cwt,tps,etc.) and fuel monitor. It will give you miles per gallon, gallons per hour, and keep track of your fuel and the cost of gas/travel. It's basically an add on DIC for cars that dont have the fancy dash displays. retail 170$.

Just my .02